Symmetric anionic polymethine dyes derived from bis(2,2,3,3,4,4,5,5-octafluoropentyl) 4,5-dinitro-9H-fluorene-2,7-disulfonate: synthesis and spectral properties

Abstract

Anionic polymethine dyes were obtained from fluorene equipped with electron-withdrawing groups (SO2OCH2(CF2)3CHF2 in positions 2 and 7 and NO2 in positions 4 and 5). Their electronic absorption spectra in various solvents were examined and compared with the spectra of related dyes derived from tetranitrofluorene and bis(2,2,3,3,4,4,5,5-octafluoropentyl) 9H-fluorene-2,7-disulfonate. The ab initio quantum chemical calculations (DFT and TDDFT at the B3LYP/6-31G(d,p) level of theory) were used to analyze the nature of electron transitions and the orbitals involved as well as the electron density redistribution in the excited state.